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Author Topic: Low charging with headlight on  (Read 1057 times)

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Offline Chuck Hahn

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Low charging with headlight on
« on: September 18, 2016, 08:15:59 AM »
In had no charging at all and the checks indicated a bad rectifier.  Replaced that and now I have excellent charging ( 14.2 at the battery ) but only when I shut off the switch that kills the headlight.  Turn the headlight back on and it drops to now higher than 12.7 no matter how fast I rev the engine.  Turn the light off and she jumps right back up.

Is this the normal way the charging system works??  Bike is a 74 CB 550 Four. Is there a wire hooked wrong at the voltage regulator maybe??  Its wired the way it was when i got the bike so maybe a PO swapped a wire around down there??  In any case, I want to get it to charge at the 14.2 with the headlight on too.  Whats the fix here????

I have done the service inspections per the manual here starting on page 93.  I note it has daylight and night time charging values...please explain this to me.  Shouldnt I be getting at least 13.8 at idle with the headlight on or off????  Im confused I guess on how the system works as far as kicking in when it senses the batterys stored voltages.

Maybe its working right..I just dont know 100%.  The battery was 100% charged because i just took it off the charger before trying out the new rectifier.

Service manual here.........
http://www.dotheton.com/downloads/CB500-550_Manual.pdf
« Last Edit: September 18, 2016, 08:30:10 AM by Chuck Hahn »
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Offline DaveBarbier

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Re: Low charging with headlight on
« Reply #1 on: September 18, 2016, 08:37:59 AM »
I would think you might have corrosion on the bullet connectors in the headlight bucket and maybe the headlight switch.

I'd wait, though, for someone smarter to confirm this :) but it's never a bad thing to go through your wire harness and clean the connections and add a bit of dielectric grease to help prevent future corrosion.
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Low charging with headlight on
« Reply #2 on: September 18, 2016, 08:54:18 AM »
Check the output rating of your bulb. Too high?
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Offline Chuck Hahn

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Re: Low charging with headlight on
« Reply #3 on: September 18, 2016, 09:41:45 AM »
How do I check that??  Numbers on it somewhere???
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Offline alacrity

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Re: Low charging with headlight on
« Reply #4 on: September 18, 2016, 01:11:08 PM »
Hey so the charging issue with these bikes are legend because there are a bunch of analog components and long runs of old wires ending with old, often corroded connectors.  And you CAN solve al the problems with time and a brain and a multimeter (and tools and a nice kit of connectors from VINTAGECONNECTIONS.com.   

My guess is you are not using the honda factory service manual for the cb500 and 550 series?  Please download it from this site now and place that Clymers (or whatever) book in the recycling bin.  Look at the bottom of p94 in the factory manual... Why am I guessing this?  Your question, "shouldn't I be getting 13.8 at idle...?" Proves to me you are not using the factory manual. Pic of p94 below.  Trust me here...   Do what it says.  THEN come back with questions if you still have em.
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Offline Chuck Hahn

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Re: Low charging with headlight on
« Reply #5 on: September 18, 2016, 01:39:15 PM »
I linked the service manual Im using in the first post........  PDF file from Dotheton.

And second..I asked the question earlier about the day and night charging thing because obviously I have the same manual your posting from.  Im not an electrical expert but I do have a meter and a brain by the way.  I just dont understand electrical theory and wire diagrams and all that other spaghetti looking graphics.

Back yourself up and look at the PDF link I posted before you go assuming I have a  Clymers manual and other crap.
« Last Edit: September 18, 2016, 02:02:17 PM by Chuck Hahn »
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Offline Bodi

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Re: Low charging with headlight on
« Reply #6 on: September 18, 2016, 02:01:42 PM »
Daytime and nighttime charging rates differ because of the headlight power, with that additional 50W+ available for charging in daytime - if your headlight is off in "daytime". I'm not sure exactly when, but vehicle regulations in Canada and the USA changed in the early 70s to require always-on headlights for motorcycles sold after some date. If yours doesn't have a headlight ON-OFF switch, that's why. The service manual for those years should show the modification (possibly a jumper in the harness somewhere to bypass the missing switch) but manuals from the internet may be from any year or a market with the switch... or Honda just didn't change the manual.
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Offline Chuck Hahn

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Re: Low charging with headlight on
« Reply #7 on: September 18, 2016, 02:08:13 PM »
This bike does have a thumb switch on the right side switch assembly  that shut off the dash and headlight.

This is the switch the bike has...EBAY picture is the same as the original thats on it now.

http://www.ebay.com/itm/Honda-CB550-CB750-Right-Side-Handlebar-Switch-Assembly-35300-341-671-/171827958126?hash=item2801be916e:g:rNkAAOSw~ZdVgCnQ&vxp=mtr
« Last Edit: September 18, 2016, 02:10:35 PM by Chuck Hahn »
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